| Molecular Formula | O3P-3 |
| Molar Mass | 78.971961 |
action
Phosphite is an auxiliary antioxidant and plays an important role in the antioxidant system. In addition to its outstanding ability to decompose hydroperoxides (which is not possible by the main antioxidant of hindered phenol), At the same time, it also has good color protection ability, which can lighten the dyeing group after the oxidation of hindered phenol antioxidant. In addition, it can also increase the processing temperature of the polymer and has a good synergistic effect with the light stabilizer. In the PVC formula, it is generally believed that phosphite mainly acts as a chelating agent. It has no obvious stabilizing effect when used alone, but it can be combined with metal soap to complex metal chloride, improve heat resistance and weather resistance, and maintain transparency. It can also be used with organotin and epoxy compounds to show synergistic effects. It can reduce the amount of main stabilizer, especially the amount of expensive organotin stabilizer.
production method
Dialkyl phosphite and trialkyl phosphite are mainly used in pesticide synthesis, and have the following general structure:
dialkyl phosphite (RO)2POH
Trialkyl phosphite (RO)3P
They can not only directly synthesize pesticide varieties, but also synthesize other pesticide intermediates, such as phosphoryl chloride, sulfur (alcohol) phosphate, etc.
The synthesis of dialkyl phosphite is relatively simple. Generally, PCl3 is directly reacted with alcohol to generate by-products hydrogen chloride and chloroalkane. When there is an acid binding agent, the reaction continues to produce trialkyl phosphite. When there is no acid binding agent, the reaction stops in the dialkyl ester stage.
PCl3 3ROH→(RO)2POH 2HCl RCl
The most widely used dialkyl esters on pesticides include dimethyl phosphite, diethyl phosphite, diisopropyl phosphite, etc., and the more widely used trialkyl esters include trimethyl phosphite, triethyl phosphite, triphenyl phosphite, etc.
The synthesis of trialkyl phosphite mainly includes direct method and indirect method.
Direct method uses phosphorus trichloride and alcohol as raw materials, and directly prepares in the presence of acid binding agent. PCl3 3ROH 3B & rarr;(RO)3P 3B HCl (B is acid binding agent)
Because the hydrogen chloride produced by the reaction will destroy the trialkyl phosphite and decompose it into dialkyl phosphite, 3mol of organic base or ammonia must be used as an acid binding agent to produce The hydrogen chloride is fixed in the form of organic alkali hydrochloride. According to the different acid binding agents used, the synthesis of trialkyl phosphite has ammonia method, tertiary amine method, tertiary amine ammonia method and other methods, of which tertiary amine ammonia method is a new process developed by combining the advantages of the first two methods.
The indirect method is also the transesterification method. First, phenol is reacted with phosphorus trichloride to generate triphenyl phosphite stable in alkaline medium, and then transesterification with alcohol in the presence of a catalyst to obtain trialkyl phosphite.
In addition, there are other methods to obtain phosphite. For example, in the presence of CCl4 and excess alcohol, 2mol alkoxide ion is used to react with crushed white phosphorus to directly produce high-yield trialkyl phosphite. If 1mol of alkoxide is used, dialkyl phosphite is obtained.